The web interface is password protected (HTTP basic authentication) and uses the system users via PAM. When deployed via Ansible, the initial user is admin with password admin. This user works for web access as well as for SSH and PostgreSQL.
To create new users, use
adduser, and add the user to the elephant-shed group.
adduser myon adduser myon elephant-shed
On RedHat/CentOS, use
vigr to add users to the elephant-shed group.